Liquid fuel supply system for internal-combustion turbines with afterburners



Nov. 10, 1953 F. H. CAREY 2,658,330

LIQUID FUEL SUPPLY SYSTEM FOR INTERNAL-COMBUSTION TURBINES WITHAFTERBURNERS Filed Nov. 2, 1948 flag? FUEL TANK /4 H5. 0 goos'rgn 3%?IDVGDIOI' PUMP F esagre/c/c ff GilQfX 8 @uawdma Attorneys CIRCULATINGPUMP Patented Nov. 10, 1953 LIQUID FUEL SUPPLY SYSTEM FORINTERNAL-COMBUSTION TURBINES WITH AFTERBURNERS Frederick Henry Carey,Gheltenham, England,

assignor to Dowty Equipment Limited, Cheltenham, England ApplicationNovember 2, 1948, Serial No. 57,842

11 Claims. 1

This invention relates to liquid fuel supply systems for aircraftinternal combustion turbine power units. One method of boosting enginethrust is to re-heat the exhaust gases after passing through the turbineand the invention is concerned more particularly with the supply of fuelto the burners provided for effecting this reheating. The thrust boostis generally required during take-ofi and may also be required undercertain conditionsof flight. The object of the invention is to providefor re-heating or after-burning in a system supplying main burners ofthe spill type and incorporating two pumps of which one serves duringnormal running to circulate fuel around a circuit including the swirlchambers of the burners and the other delivers into this circuit fuel inexcess of the capacity of the circuit so as to cause correspondingamounts to issue through the burner orifices. Such a system forms thesubject of my Patent No. 2,608,247, issued August 26, 1952. Theadvantage of such a system is that the pump which causes the fuel tocirculate, hereinafter referred to as the circulating pump, although notby itself causing fuel to issue through the burner orifices, ensureseffectual atomization of any fuel delivered into the circuit by theother pump, hereinafter referred to as the supply pump. Thus, even atlow engine speeds, the fuel injected into the circuit by the supply pumpis properly atomized and a sensitive control of the engine speed isobtained.

The invention makes use of the fact that the thrust boost is requiredonly at maximum throttle openings at which the flow from the supply tomeet engine requirements is sufficient to ensure satisfactoryatomization and the circulating pump has lost its primary function.According to this invention, therefore, in a fuel supply system of thekind referred to and incorporating .burners for re-heating the exhaustgases for the purpose of providing thrust boost, the capacity of one ofthe pumps, e. g. the circulating pump, is utilised when thrust boost isrequired in order to supply fuel to the re-heating burners while themain combustion chamber burners receive their fuel from the other pump.

When the main spill burners are being supplied with fuel from say thesupply pump only, .i. e. during thrust boost, the common return linefrom these burners may be closed, for example by means of a non-returnvalve, so that the burners may function as simple direct injectionnozzles.

The burners of the after-burning system may themselves be either of thespill type or of the direct-injection type, and the capacity of the pumpused for feeding these burners may in some cases be supplemented by anauxiliary pump of any desired capacity.

When the circulating pump is to feed the burners of the re-heatingsystem, the pilot may effect the necessary change in the main system bymoving his engine control lever or throttle lever beyond its maximumthrottle setting to bring about movement of what may be termed achange-over valve, which movement isolates the circulating pump from themain burners and places it in communication with the re-heating burnersand with a source of supply of fuel. The isolation of the circulatingpump from the main burners may automatically close the return line fromthe latter.

A fuel system in accordance with the invention will now be described byway of example with reference to the accompanying diagrammatic drawing,of which Figure 1 shows one system with the parts in the positions theyoccupy during re-heating;

Figure 2 is a fragmentary view showing a detail in the position itoccupies during normal engine running; and

Figure 3 is a modification.

Referring to Figures 1 and 2,'the system there shown includes mainburners of the spill type, one of which is shown at l I, a circulatingpump I2 for circulating fuel around a circuit including the swirlchambers of the burners I l, a supply pump I3 for feeding fuel from atank l4 through a throttle control 15 into the circulating flow set upby the pump [2, re-heating burners of the spill type (there are usuallytwo, of which one is indicated at l6) a change-over valve IT, a relayvalve l8, and a solenoid valve I9.

The change-over valve I! has four lands and during normal enginerunning, 1. e. when there is no supply to the re-heating burners l6,occupies the position shown in Figure 2 by virtue of pressure appliedagainst the lower end of the valve member from the tank booster pump Ma.The electrical windings (not shown) of the solenoid valve l9 areincluded in an electrical circuit having a switch (not shown) housedwithin the throttle casing l5 and closed whenever the throttle lever 20is moved beyond the maximum throttle setting, in the throttle openingsense which maximum setting is indicated in Figure 1 in dotted lines.When the lever 20 is moved in the trottle opening sense beyond themaximum throttle setting, through the side step 2| of the throttle gate,to the full line position shown in Figure 1, the switch closes so thatthe solenoid coil is energized to trip the valve element of the solenoidvalve I9 into the right-hand position shown in Figure 1. It will be seenthat when the solenoid valve is in this position, fuel passes from thesupply pump I3 through the throttle 15 to enter the valve chamber 22 bya conduit 23. From the chamber 22 the fuel passes by a conduit 24 to actupon one end of the relay valve I8 to shift the valve element against aspring 25 in order to place a conduit 26 in communication with a branchconduit 21 leading from the conduit 23. Movement of the relay valve I3therefore permits fuel from the supply pump I3 to reach the upper end ofthe change-over valve I1 which shifts the latter from the normal runningposition shown in Figure 2 against a fixed stop 43 into theafter-burning or re-heating position shown in Figure 1. The variousvalves will remain in this position so long as the solenoid winding isenergized by the position of the throttle lever 20. In addition toacting upon the valve I'I, fuel from the supply pump I3 will be fed tothe main burners II along a conduit 23. Although the burners II are ofthe spill type they will function during the re-heating operation asdirect injection nozzles on account of the return line 23 being closedby the land 30 of the changeover valve. The re-heating burners I receivefuel from the circulating pump I2 which feeds along a conduit 3i througha section of the change-over valve I1 and through a conduit 32. Duringthe re-heating operation the circulating pump I2 is supplied with fuelfrom the tank I4 through conduits 33, through the change-over valve I1,and through a conduit 34. The return line 35 from the burners I5communicates with the inlet of the circulating pump I2 and includes arestrictor 35 and a non-return valve 31.

As soon as the throttle lever 23 is pulled in a throttle closing senseto or beyond the maximum throttle setting indicated in dotted lines, the

switch of the solenoid valve I! will open and the solenoid valve elementwill move to the left under the influence of a spring toclose the end ofthe conduit 23 and to place the conduit 24 in communication with aconduit 39 leading to the low pressure zone above the fuel in the tankI4. The relay valve I8 will thereupon move to the left by the spring 25to place the conduits 26 and 21 in communication with the conduit 39just referred to so that the pressure above the change-over valve I'Ifalls and the valve II rises into the position shown in Figure 2, underthe influence of pressure acting on the valves lower end, supplied fromthe booster pump Ma.

The booster pump I4a, being driven independently of the engine, servesat all times to prime the supply pump I3. During the reheating operation(Figure l)- the booster pump I4a primes the pump I2, also, by way ofconduit 33, the lower portion of change-over valve I1, and conduit 34,although under normal running conditions (Figure 2) the pump I2, or thelatters intake side which is included within the circulating path whichpump I2 keeps filled, is supplied excess fuel in controlled amounts bythe supply pump I3, and so needs no supply from booster pump I4a(otherwise than indirectly via pump I3) and is not so supplied. Thebooster pump is of a type such that, in case it fails, it will not blocksupply to the pump or pumps which it primes, thus to starve it or them.

Normal running ensues as soon as the changeover valve I'I reaches theposition shown in Figure 2. In this position the pump I2 circulates fuelaround a closed and completely filled circuit including the conduit 3|,the uppermost portion of the change-over valve, the conduit 28 to theswirl chamber of the main burner II, and thence via conduit 29, and backto conduit 34 and the low-pressure side of the circulating pump by wayof a second portion of the change-over valve. The supply pump continuesto receive fuel from the booster pump a, which it delivers past throttleI5 and through conduit 23 as far as the branch conduit 40 and then intothe change-over valve, in the same portion of that valve as is at thetime included within the closed circulation path of the pump I2. Theamount of fuel added at this point from the pump I3 to the closedconduit overfills the latter, and effects corresponding discharge at theorifice of the main spill burner l I. In other words, the supply pumpnow feeds to the inlet of the circulating pump. This system willcontinue to function for normal running for any position of the throttlelever 20 at or below the maximum throttle setting of the lever but assoon as the lever 23 is moved through the step in the gate the solenoidvalve will be energised and the system will again become as shown inFigure 1 in which the main spill burners are functioning as directinjection nozzles and the re-heating burners are being suppliedwith'fuel.

Referring now to the modification shown in Figure 3, the re-heatingspill burners it of Figure 1 are replaced by simplex or direct injectionburners 4| and in place of the restrictor 36 and the non-return valve 31there is provided an altitude control between the conduits 32 and 35.The conduits 42 and 43 of Figure 3 can be regarded as continuations ofthe conduits 32 and 35 respectively of Figure 1 with the burners I6omitted. The altitude control comprises an aneroid-controlled releasevalve 44 associated with a pressure-regulating by-pass valve 45. For anygiven altitude the pressure required to unseat the release valve 44 willbe constant which will determine the constant pressure in the conduit 45leading from the valve 45 to the burners 4|. Variations in altitude willthrough the aneroid vary the pressure at which the release valve 44unseats which in turn will vary the pressure in the conduit 43correspondingly. The supply of fuel to the re-heating burners U willthus be regulated in accordance with altitude; it being understood thatless fuel is needed with higher altitude.

An altitude control such as that shown in Figure 3 may also be providedacross the conduits 3'2 and 35 of Figure l with the restrictor 36omitted.

If it is desired to supplement the capacity of the circulating pumpduring re-heating, there may be provided an auxiliary pump controlled byan additional land on the change-over valve so that said auxiliary pumpoperates in parallel with the circulating pump during re-heating.

If the circulating system for the main burners is designed for emergencyoperation in accordance with co-pending United States application SerialNo. 2,342, filed January 14, 1948, it is feasible to utilise thecapacity of the supply pump for feeding the re-heating burners duringre-heating and to use the circulating pump for feeding the main burners.

Basically the invention utilises for feeding the after-burners, one ofthe two pumps essential to the circulating system for the main burners,and

shiftable between a normal-running and a reheating position,respectively, and a closed circuit including said circulating pump andsaid changeover valve but excluding said supply pump, said closedcircuit including a supply conduit leading from the circulating pump tothe change-over valve and thence adapted for connection to the mainburner nozzle for supply of fuel to the burner nozzle under normalrunning conditions, and including also a return conduit from the mainburner nozzle to the change-over valve and thence to the intake side ofthe circulating pump,

for return of fuel to such pump under normal running conditions, adelivery conduit leading from said supply pump to a connection at saidchange-over valve with said closed circuit for delivery into the latter,during normal running conditions, whereby to effect correspondingdischarge at the main burner nozzle, throttle means operativelyconnected in said delivery conduit intermediate the supply pump and saidconnection at the change-over valve to the closed circuit, and movableto vary the effective delivery from said supply pump between a minimumand a normal maximum limit, and on beyond in the throttle-opening senseto an abnormal maximum limit, a branch line leading from said deliveryconduit, at a point beyond the throttle means from the supply pump, to aconnection at the change-over valve to the main burner supply conduit, areheating burner'supply line extending from said change-over valve andadapted to be connected to the reheating burner, a low pressureconnection adapted to be connected to a fuel source and extending tosaid supply pump and also by way of said change-over valve to aconnection with the circulating pumps intake, and a reheating burnerreturn line leading to said change-over valve, said change-over valveand its valve body being so organized and arranged that, when in thenormal running position it maintains the closed circuit open forcirculation of fuel from the circulating pump to the main burner nozzleand return, and the delivery conduit from the supply pump open toaugment the fuel in said closed circuit, for corresponding discharge atthe main spill burner, and further organized and arranged, when in itsnormal running position, to close the branch line connection from thesupply pump to the main burner supply conduit, and to close also thereheating burner supply line and the low pressure connection to thecirculating pumps intake, and the reheating burner return line, andmeans operatively connected to said throttle means, arranged andoperable by movement of the latter past the normal limit in thethrottle-opening sense, to shift said change-over valve body into itsreheating position, said change-over valve being further organized andarranged that, in such reheating position, it interrupts said closedcircuit and said delivery conduit, and connects the circulatin pump onlyto said reheating burner supply line for delivery to the'reheatingburner, and to said low pressure connection for fuel supply, and saidreheating burner return line to the circulating conduit and circulatingpumps intake, and being further organized and arranged to connect saidsupply pump only to said branch line and thence at the change-over valveto the main burner supply line for delivery'to the main burner nozzle,and to close the return conduit from the'main burner nozzle, said meanswhich are operatively connected to the throttle means being operativeconversely, upon movement past the normal limit in the throttle-closingsense, to shift the changeover valve back into position to restore theinterrupted or altered conduits for normal running.

2. The combination of claim 1, including a fuel source and a boosterpump operatively associated therewith and connected at all times to thelow pressure connection and thereby to the intake of the supply pump, alow pressure branch connection from said low pressure connection to thecirculating pump by way of said throttleoperated means, the latterhaving elements normally closing off said branch connection, but saidthrottle-operated means being arranged to open the low pressure branchconnection automatically upon movement of the throttle means beyond thenormal maximum limit, to connect the booster pump discharge into theclosed conduit which at such time includes the circulating pump and thereheating burner, for spill type operation of the latter burner.

3. The combination of claim 1, wherein the throttle-operated meansincludes a solenoid valve yieldingly biased into a normal, position, andoperatively associated valve means normally held in position to closeoff delivery from the supply pump to the reheating burner, andelectrical control means for said solenoid valve operatively connectionfor operation by said throttle means, arranged for energization of thesolenoid and shifting of the solenoid valve and of the associated valvemeans controlled thereby, upon movement of said throttle means beyondthe normal maximum limit in the throttle opening sense, to connect thedischarge from the supply pump to the means which is operativelyconnected to said throttle-operated means, to shift the latter andthereby to isolate the two pumps, to close the normal return line of thecirculating pump, and to supply fuel from the supply pump to the mainburner nozzle, and from the circulating pump to the reheating burnernozzle.

4. The combination of claim 1, characterized in that the reheatingburner is of the direct injection type, a pressure control by-pass valvein the reheating burner supply line, an aneroidcontrolled release valveoperatively connected to said pressure control by-pass valve, toautomatically regulate supply to the reheating burner, when the latteris operative, in accordance with altitude effects.

5. In combination with a main burner of the spill type and an exhaustreheating burner of an aircraft internal combustion turbine engine,

a fuel source, a circulating pump, a first conduit means for circulatingfuel in a normally closed circuit which includes said main burner andsaid circulating pump, a supply pump, a second conduit means forcirculating fuel abnormally in a closed circuit which includes saidsupply pump, part of said first conduit means, and said reheatingburner, a change-over valve arranged in common in and including elementscontrolling assasso each of the two conduit means, andshiftable from anormal position wherein the supply pump is connected into the closedcircuit of the circulating pump for augmentation of the supply to themain burner, and is closed off from the reheating burner, into anabnormal position wherein return from the main burner is cut off, thedelivery from the circulating pump and the return thereto are connectedto the reheating burner, and the delivery from the supply pump isconnected to the main burner, means including a throttle lever forregulating supply of fuel from the supply pump to whichever burner isconnected to the latter for supply, said throttle lever being shiftablethrough a normal range and also, therebeyond in the throttle-openingsense, through an abnormal range, and means operable by movement of saidthrottle lever into its abnormal range to shift said change-over valveinto its abnormal position, or upon return of said throttle lever to itsnormal range to shift said change-over valve into its normal position.

6. The combination of claim 5, including a booster pump operativelyassociated with said fuel source, and for delivery to said supply pumpand, in the abnormal position only of the changeover valve, by way ofthe latter to the closed circuit which then includes the circulatingpump and the reheating burner, for augmentation of supply to the latter.

7. The combination of claim 5, wherein the throttle lever operable meansincludes a solenoid valve yieldingly biased into a normal position, andconnected to the throttle lever for electrical operation upon movementof said throttle lever into its abnormal range, into an abnormalposition affording connection of pressure fluid from the supply pump tothe change-over valve, to initiate movement of the change-over valveinto its abnormal position.

8. The combination of claim '7, including also a relay valve yieldinglybiased into a normal position, and in communication with the deliverypressure from the supply pump by way of the solenoid valve upon movementof the latter into its abnormal position, to connect the supply pumpdelivery to the main burner.

9. In combination with a main burner of the spill type and an exhaustreheating burner of the direct injection type, of an aircraft internalcombustion turbine engine, a fuel source, a circulating pump, a firstconduit means for circulating fuel normally in a closed circuit whichincludes said main burner and said circulating pump, a supply pump,normally connected to said first conduit means to augment supply to themain burner, a second conduit means for delivering fuel abnormally fromthe supply pump to the main burner by way in part of the first conduitmeans, and from the circulating pump to the reheating burner, also byway in part of the first conduit means, a change-over valve arranged incommon in and including elements controlling each of the two conduitmeans, and shiftable from a normal position wherein the two pumpscooperate to supply fuel to the main burner, and fuel supply to thereheating burner is cut off, to an abnormal position wherein the pumpsare isolated, and supply the one the main burner and the other thereheating burner, a throttle lever shiftable through a normal range andalso therebeyond in the throttle-opening sense through an abnormalrange, means including said throttle lever for regulating supply of fuelfrom the supply pump, and operable 8 automatically upon movement of thethrottle lever into its abnormal range to shift the changeover valveinto its abnormal position, and an aneroid-controlled release valve inthe second conduit means, and a cooperating pressure-controlled by-passvalve, to regulate supply to the reheating burner, during abnormaloperation, automatically in accordance with pressure altitude.

10. A liquid fuel supply system especially for aircraft engines, for thecontinuous supply of fuel to an atomizing main burner nozzle of thespill type, but which is capable of functioning as a direct injectionnozzle, and for the occasional supply of fuel to an exhaust reheatingburner also of the spill type, which system comprises a change-overvalve housing and valve body therein shiftable between a normal runningposition and a reheating position, supply and return conduits eachextending by way of said valve housing to define, when said valve bodyis in normal running position, a primary closed circuit which is freelyopen and adapted to be connected, at a first side of the valve housing,to the main burner nozzle for delivery of fuel thereto and return offuel therefrom, a circulating pump included in said closed circuit at asecond side of the valve housing, opposite said first side, and of suchcapacity relative to the supply and return conduits as to maintain thecircuit and the main burner nozzle substantially full to the point ofoverflowing without itself causing any discharge therefrom so long asthe valve body is in normal running position, a supply pump locatedexternally of said circuit and adapted to be connected to a supplysource, a delivery conduit leading from said supply pump and connectedby way of said valve housing for delivery into said closed circuit, whenthe valve body is in its normal running position, to augment the supplywithin the closed circuit and to efiect corresponding discharge at themain burner nozzle, throttle means operatively connected in saiddelivery conduit and movable to vary the effective delivery from saidsupply pump between minimum and a normal maximum limit, and on beyond inthe throttle-opening sense to an abnormal maximum limit, a reheatingburner supply conduit leading from and a reheating burner return conduitleading to the valve housing, and each adapted to be connected to thereheating burner nozzle for delivery of fuel thereto and return of thefuel therefrom, and to define with that portion of the aforesaid closedcircuit which is at the second side of the valve housing a secondarycircuit which is closed for continuous circulation when the valve bodyis in its reheating position, said valve body being formed and arrangedto close said secondary closed circuit and to establish said primaryclosed circuit, including the circulating pump, and to connect saiddelivery conduit to said primary closed circuit, so long as such valvebody remains in normal running position, and to interrupt said primaryclosed circuit and to establish said secondary closed circuit when thevalve body is in reheating position, a branch line leading from saiddelivery conduit, beyond the throttle means from the supply pump, to themain burner supply duit by way of said valve housing, a low pressureconnection adapted to be connected to a fuel supply source and extendingto said valve housing, the valve body being further formed and arrangedto close said branch line and said low pressure connection so long asthe valve body is in normal running position, and to establishcommunication between the branch line and the main burner supplyconduit, and between the low pressure connection and said secondaryclosed circuit to augment the supply in the latter, for spill dischargeat the reheating burner, when the valve body is in reheating position,and means operatively connected to said throttle means, for operation bymovement of the latter beyond its normal maximum limit in thethrottle-opening sense, to shift said valve body into its reheatingposition, and conversely for return of said valve body to its normalrunning position by return movement of the throttle means Within itsnormal operating limits.

11. A liquid-fuel supply system as in claim 10, wherein the meansoperatively connected with the throttle means includes a. solenoid valvein said branch line normally closed to interrupt supply by way of saidbranch line to the main burner supply conduit, electrical meansoperatively connected to said solenoid valve, and to 10 the throttlemeans to open the solenoid valve upon movement of the throttle means inthe throttle-opening sense beyond its normal maximum limit, a relayvalve biased into a closed position, means controlled by opening of saidsolenoid valve to open said relay valve, and a pressure line connected,past said relay valve, to said change-over valve to shift the latterautomatically from its normal running position upon opening of the relayvalve.

FREDERICK HENRY CAREY.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,238,905 Lysholm Apr. 22, 1941 2,506,611 Neal et a1 May 9,1950 2,520,967 Schmitt Sept. 5, 1950 2,523,214 Ifield Sept. 19, 19502,537,681 Lawrence Jan. 9, 1951

